Fiber reinforced composite materials produced by using an epoxy resin composition for their matrix resin are used in a wide variety of industrial applications including aircrafts and automobiles since they have excellent mechanical properties. In particular, fiber reinforced composite materials are finding an increasing use for a surface plate of a honeycomb panel in structural materials and interior materials of aircrafts to respond to weight reduction requirements.
In the production of honeycomb panels, further reduction in weight and cost is currently required, and there is a strong demand for the so-called “self-adhesion technique” in which the honeycomb core and the prepreg are directly adhered.
In order to realize such “self-adhesion” of a prepreg, juncture of the honeycomb core and the prepreg is wetted by the resin from the prepreg in the course of curing by heating to thereby form a resin reservoir called “fillet”.
JP 2-305860 A discloses an attempt to provide a thermosetting resin composition, a cured product thereof, and a prepreg and a fiber reinforced plastic produced by using such resin composition for the matrix resin, which exhibits excellent properties such as high toughness, high elongation, and low internal stress simultaneously with high strength, high modulus, low water absorption, high heat resistance, and good working efficiency, and wherein such properties are highly stable. More specifically, JP 2-305860 A discloses “a resin composition comprising the following components [A], [B], and [C]:
[A]: thermosetting resin,
[B]: curing agent, and
[C]: thermoplastic resin
as its critical components, wherein the component [C] is a block copolymer or a graft copolymer comprising a chain compatible with the component [A] or [B] and a chain incompatible with the component [A] or [B]”.